4.9GHz on R52Hn?

Will R52Hn do 4.9 GHz with an unlock code or something?

Nop, coz its public safety frequency (police, fire dep, emerency ect.)

4920-6100 with superchannel

superchannel is included in all v4 installations. just change wireless mode to superchannel and see “/interface wireless info print” to view all available frequencies

it will be available and if I upgrade an older RouterOS?

yes

COOL I have way too much interference, my client is local government