Can I add a 3rd follow-up message to an existing sequence on Starter Plan?

Hi.

I'm currently running a sequence on the Starter plan with this structure:

• Connection Request (Send Invitation)
• Follow-up 1 (first message after acceptance)
• Follow-up 2 (second message)

I want to add a Follow-up 3 (third message after connection) as a final touchpoint.

Two quick questions:

1. Does the Starter plan's "Basic message sequences" feature allow 3+ follow-up messages, or is there a limit on the number of steps after the initial connection?
2. If I edit my existing sequence to add this third follow-up, will it apply to contacts already progressing through my current sequence, or only to new contacts enrolled after the change?

Also, whilst I'm here: I'm concerned about automated messages being sent after I've already started a conversation with someone. Does Botdog's reply detection definitely stop the sequence once someone responds?

Thanks in advance!