Section 21 and pre-2015 tenancies

Tenancy Types and Management

I appreciate there aren't very many tenancies left that pre-date 2015 but I have purchased a property with a sitting tenant. The AST was created in 2007 and hasn't been updated to my knowledge.

I have no documentation from the previous landlord except the AST.

Am I correct in thinking that the requirement to have provided gas safety certificates, an EPC, How to Rent guide does not apply, and not having provided these will not prevent me from obtaining possession under Section 21?

With respect to the deposit, there is no evidence of one having been paid at the time the AST was created. If it transpires that a deposit was paid to the previous landlord, obviously I cannot show it was protected. If I return the sum to the tenant, or protect it, within 31 days of purchasing the property, can I still use Section 21?