Where is $MALT$ (Mucosa-Associated Lymphoid Tissue) located?

The immunity obtained after the body has recovered from a disease is

In which type of acquired immunity are ready-made antibodies introduced into the host body?

What is the full form of $HLA$?

Which type of cells produce an army of proteins to fight against pathogens that have entered our body?

$A$: Live attenuated vaccine is better in terms of immunity provided to the recipient.
$R$: As secondary lymphoid organs,example $Peyer's$ patches are stimulated to protect the individual.