"till now" and "so far" The two phrases overlap in meaning, but they also have a different usage. "until now" (more natural than "till now" in my opinion) is more general in meaning. You can use it for pretty much anything that happened in your life. For example, you might say "I've never thought about it that way until now", "I've never tasted this kind of food until now". "so far" seems more specific and purposeful. It works better with something you started at some point with a purpose. So if you've joined a new company, you might say "So far, things are going well at work". With your new boyfriend, "So far, so good", etc. Your sentence "Till now, I've practised 3 times" is also specific to whatever you're practicing. So "so far" is better in my opinion.

I'll also add that 'until now' is usually used to mean that something was a certain way until this point in time, but now it is different. Example: I had never eaten mapo doufu until now. This means "Before this point in time, I did not eat mapo dofu, but now I am eating it."

To me, 'Till' is incorrectly spelled slang and is not a good choice to use in a written sentence unless you are quoting someone's speech or you are a poet/artist and purposefully using ( 'til ) to make a point. Utilizing the full word ''until now' could be used interchangeably with 'so far' easily.

"till now" is a shortened form of "until now", mostly used while speaking. As far as I know there is no difference in meaning, but so far reads a lot better in a written text.