For the air filter, take it off, use some sand paper to clean the rusty spots, then buy abro engine enamel and spray paint 3 coats. I just did it in khyber.
The pipe going to water body isn't that expensive. A few hundred rs. You can find it easily in plaza market. Various shops. I am forgetting the one I bought from. Radiator guy or the mechanic will fit it properly. Use proper glue/silicone to stick it. Ask seniors what should be used here. My guy used silicone apparently. No leaks so far.
For rusty spots, same solution. Clean it mildly with zero number sand paper then ask the denter to apply primer and then paint. If you apply paint and primer yourself, the finishing won't be as good as the denter would do.