If two proteins have half of the total sequence same, would these two proteins function in a similar function?

Answer 1

Even if they have 50% the same, all bets are off. Example: Penicillin-binding protein. Bacteria constantly evolve new sequences to change D-alanine-transporting-protein into PBP. PBP kills penicillin. The D-Ala-transporter keeps on functioning.

I put your question: Do these two proteins function in a similar function? Do they function in a similar way?

Answer 2

Not necessarily. The devil is in the details, and just because one part behaves in a particular manner doesn't say a thing about what the other part will do.