Chain adjustment..?

Howdy peeps - when i use my rear brakes my bike sounds as though i’m downshifting very badly and it does not skid (not that i’m trying to skid) as it should when you slam on the brakes.
Also sometimes when shifting gears i have to give it a sort of hard flick otherwise it tends to try & shift but gets stuck between two gears.

The chain looks a bit loose & my first guess is it needs a chain adjustment?

Any further ideas?

Cheers!

clutch adjustment.

& rear pads…

all of the above. and perhaps a major service.

Turns out it was ABS - phew…feel silly not realizing my bike had ABS on the rear brakes as well as the front…thought it was only the front…