I’m sure this is “101” for everyone reading this 

“…you must spend your action each turn casting the spell, and you must maintain your concentration while you do so” (PHB p. 202)

”Normal activity, such as moving and attacking, doesn’t interfere with concentration” (PHB p. 203)

If spell casting PC has an attack Bonus Action yet uses their Action to cast a spell as a Ritual

Can they still attack?

This is an odd scenario.

Typically when a spell has a casting time longer than one action it is measured in minutes. One minute is ten rounds so these spells usually aren't worth casting in combat.

Casting a spell as a ritual adds ten minutes to the cast time, or a hundred rounds in other words.

Another common thing to be aware of is many Bonus Action attacks like Two-Weapon Fighting require you to also attack with your action.

Finally, a specific spell might have requirements that make casting it in combat more difficult. Teleportation Circle for example requires you to draw a circle and runes on the ground as part of casting the spell.

Otherwise if the character has a way to attack with their bonus action I don't see anything in the rules that would prevent them from doing so while casting a spell with a long casting time.

Good point re: BA Two Weapon Fighting

Thanks

Spending an action to cast a spell with a longer casting time doesn't otherwise prevent you from taking bonus action, reaction or other action if you have any.

Yes, but 99% of the time the ritual is going to be interupted because:

1) Takes way too many rounds to complete (100)

2) You only have a Bonus action to do anything with

3) You can't cast any concentration spells

4) Any attack that does damage will require you to make a concentration check or mess up the ritual casting.

If you have a standard bonus action attack, you can use it. Something like Scimitar of Speed

However, you cannot cast a bonus action spell without disrupting the ritual. 

I guess casting a spell as a Ritual set aside

If PC casts a spell which last for 1 minute (10 rounds)

And wants to cast spell for full Duration

Does the PC have to choose Cast A Spell as their Action each turn to maintain Concentration

Or could PC cast the spell on their turn, maintain concentration by making the CON save when they take damage

And choosing an Attack or another Action on their next turn

Or would PC’s next turn have to be Cast A Spell to have the continued effect of the initial Spell they cast?

"When you cast a spell with a casting time longer than a single action or reaction, you must spend your action each turn casting the spell, and you must maintain your concentration while you do so. "

You have to both spend your action and also separately not lose concentration. The casting time is how long it takes for the spell to start taking effect, the spell is still in progress until the casting time is completed.

Wait so the spell’s Duration is the amount of time before the spell kicks in & takes effect?

I was under the impression that the spell takes effect immediately upon casting then lasts for the Duration

Also, what about this quote re: Concentration?

”Normal activity, such as moving and attacking, doesn’t interfere with concentration” (PHB p. 203)

Quote from eightyocho >>

Wait so the spell’s Duration is the amount of time before the spell kicks in & takes effect?

I was under the impression that the spell takes effect immediately upon casting then lasts for the Duration

 No he said Casting Time, not Duration. Separate concepts that does separate things. The Duration doesn't start until the Casting Time has been completed, which for some spells (ritual spells among them) can take some time.

A spell that lasts for 1 minute is different than a spell that takes 1 minute to cast. When you said "If PC casts a spell which last for 1 minute (10 rounds) And wants to cast spell for full Duration" that's kind of ambiguous, and I took it, based on the second half, to mean 'if a PC casts a spell that takes a minute to cast and so wants to spend that full minute doing the casting.'

Basically, if the casting time is 1 action or longer then in order to not stop the casting and losing the spell without it completing, each round you still have to use your action to cast the spell, and cannot lose your concentration. Once the spell is finished being cast and goes into effect, you can use your action for whatever you like, as long as you don't do anything to break your concentration, which includes casting another spell with concentration, taking damage and failing the resulting CON save, or being incapacitated.

Quote from eightyocho>>

“…you must spend your action each turn casting the spell, and you must maintain your concentration while you do so” (PHB p. 202)

This is specifically regarding a spell with a Casting Time of longer than 1 Action, or has been made so by casting it as a Ritual. While casting such a spell the caster must spend their Action to cast the spell every turn as well as maintain their concentration.

”Normal activity, such as moving and attacking, doesn’t interfere with concentration” (PHB p. 203)

If spell casting PC has an attack Bonus Action yet uses their Action to cast a spell as a Ritual

Can they still attack?

They can if they have some way to attack without taking the Attack Action, because their one Action per turn is taken up with casting the spell. If they do not take the Cast a Spell each Action, they will lose the spell they are trying to cast. But again, this is only in the specific case of trying to cast a spell that has a Casting Time of longer than 1 Action or has been made to take longer than 1 Action by casting it as a ritual.

Normal activity such as attacking not breaking concentration is relevant when a spell has already been cast and has a Duration of Concentration, which usually means that it is a spell that lasts until it's stated duration or until the caster's concentration is broken, whichever comes first.

A number of things require concentration, but they are not the same things. In this case you have brought up two different and separate cases which depend on concentration:
1) During the entire casting of a spell which has a Casting Time of longer than 1 Action, or which has been made to have that by casting it as a ritual
2) Maintaining the duration of a spell which has Duration: Concentration

Does that make sense?

This is exactly what I was thinking

What others have said seemed either contrary to this or perhaps I just didn’t fully understand their explanation 

Your explanation here is what I deduced but wasn’t 100% certain

The verbiage in these books can be a bit tricky 

Thanks for the clarity 🙏🏾 

Ahhh he DID say that

Good catch 😉 

I get it now 👍🏾 

And keeping concentration basically means not being incapacitated 

Or making the CON save, correct?

Quote from eightyocho >>

And keeping concentration basically means not being incapacitated 

Or making the CON save, correct?

https://www.dndbeyond.com/sources/phb/spellcasting#Concentration