Thanks a lot bluppfisk! I appreciate.

@yankee00

I think you owe us all drinks for solving your cabinet and smell problems haha.

I'll be happy to pay for a round. Get that pig roasting!

I have found with some budget silicon sealer (anti-mold type), if it is not the one that stinks like vinegar when new, has a dusty smell. It takes a long time to go away.

To be clear, if I buy anti-mold silicon sealer, I want one that does smell like vinegar. That's the good one right?

So is the budget BQ brand of anti-mold a good or dusty smell leaving one?

Yep, the cheap B&Q own brand stinks dusty for months. I made that mistake.
Use the Pattex or one of the similar priced brands. Or if it is not your place and you will be leaving in 12 months, just get the regular silicon sealant.

does anyone have a number to a plumber that can take out the toilet and put a sealant there if it doesn't exist? possibly check if there are P-traps/s-tubes installed under the drains?

The trick is indeed S tubing known as well as swan-necks. Often the sink drains don't have them so you can make your own by using a flexible drain pipe and getting a nice S bend in it. Make sure the end of the pipe at the bottom is properly sealed so no smells can pass.

For toilets it is a bit more complicated. The toilet pot has its own S bend build into the pot. This is then standing on a drain that has a U bend. That makes two in a row and this makes the system to malfunction; that is the flushing does not work properly. Therefore there should be an air gap between the two bends. This is usually achieved by not completely sealing the toilet pot to the ground so air can move between the two bends freely. In this lays as well the problem. The pot not always drains nicely into the pipe under it and faecal matter ends up between the toilet pot and the floor and this creates the stink.
Most people will solve this by rekitting the pot but then the flushing is not working properly. The trick is to get the toilet pot aligned as best as possible and make a little dike with silicon around the hole in the floor. Make sure that air can still enter by not completely gluing the pot to the floor (Leave an air gap at the back) and make sure your drain from the toilet pot is not completely glued all around to the hole.
These air gaps are really necessary for a proper flush and without a proper flush the changes of faecal matter ending up between the pot and the floor increases.

SO MAKE SURE YOU LEAVE AIR GAPS (also this might look counterproductive it really is necessary and works.).

The other thing I have seen is that the old squat toilet is left in place, part tiled over and a western style sit toilet is installed on top. You can see if this is the case as there is normally a step up to the throne.
If you have a squat toilet, then it will usually have an S or P trap installed. But the sink waste pipe shares the same external pipe, and so the smell is coming up through either that pipe, or even the drains in the floor or shower.

The drains in the floor or shower can be modified by an aftermarket pipe that you just pop down the hole. This aftermarket thing has a water trap in it that stops the vapours, but needs clearing a lot.

thanks lemon lover and tigertiger. Those two things are exactly my issues that I will need to made sure happens. The question is WHO can I ask to do this for me?