1) I have no intention to settle in the UK. Will this settlement visa enable me to travel back and forth between the UK and my home country whenever I want?
Probably not. One of the requirements for the visa is
You and your partner must intend to live together permanently in the UK after you apply.
At some point, it is likely that an immigration officer will notice that you are not living in the UK. If that happens, it is likely that your visa will be revoked.
2) My employer is based in my home country and has clients across the UK and other parts of the world. Will this settlement visa enable me to visit my clients in UK - Or should I take another visa to visit my clients?
Depending on what you're doing during those visits, you may want a standard visitor visa instead.
3) Can I work from the UK for my employer who is based in my home country?
If you actually move to the UK, you certainly can. If your visa is revoked, you certainly cannot. If your visa is not revoked, but you use it in a manner inconsistent with its requirements, then it's not quite clear. The visa does authorize work, so you would probably avoid any sanctions for work undertaken in the UK before the visa is revoked.
4) My visa is valid for 3 years, so what will happen after 3 years?
You will have to apply to extend the visa at that point, which seems unlikely to succeed given your lack of intent to settle in the UK.