It's impossible to rotate any one centre 90 degrees without affecting another.
Basically there have to be an even number of 90 degree turns. For example, rotate up and right 90 degrees, or up and down 90 degrees, or up and right 180 degrees or just rotate up 180 degrees.
To rotate R, R2 or R' and U' U2 or U (so one goes clockwise the other anticlockwise)...
RL', FB', UD', (R, R2 or R' - you choose), LR', BF', DU' (U', U2 or U - depending on which you picked for the middle choice).
To rotate U2 only...
(RL, U2, R'L' U) x2.
There are algs for U and D, but I never needed them, so I never learned them.
Please take off topic discussion off this forum. Thanks.