The life of an engine totally depends on how it has been maintained. In your example I have seen some cars with essentially the same engine clocking over 200k Kilometers and some which cough and breakdown even before hitting 100k so its very hard to ascertain details about your first three questions.
What you can do is join a Suzuki Swift owners club or something or something similar to know the typical life of components and I think you will get what you are looking for.
Your final question has been answered by Solar Mike in the comments.
Below are a few reasons why you might be experiencing power drop due to general wear and tear , this however is not specific to your engine but a general checklist.
Note: since you have told you do not see any smoke from your exhaust , I am ruling out gasket issues.
- Loss of compression : With old age the piston rings will wear and it will result in derease in engine compression and as we all know if the air + Fuel mixture is not compressed to its optimum pressure you will experience loss in performance and economy.
- Cogged up Fuel / Air supply : Sometimes the issue is just minor like a clogged up air filter or a bad fuel pump or leak in the lines or something like that.
