Re: ~urdu~…
Yes, you can use “aap” for people younger than you, it’s just more respect.
SaarRDhey aik ya 2 wagera isliye nahi hotey kyon k jiss ney SAB SEY PAHLEY Urdu mein time bataya tha, usney yeh alfaaz istimaal nahi kiye hongey 
Re: ~urdu~…
Yes, you can use “aap” for people younger than you, it’s just more respect.
SaarRDhey aik ya 2 wagera isliye nahi hotey kyon k jiss ney SAB SEY PAHLEY Urdu mein time bataya tha, usney yeh alfaaz istimaal nahi kiye hongey