The catch is of course the language barrier making everything a little bit inconvenient, and that the cost of living is likely to seem outrageously high compared to what you're used to (but still affordable if you can find at least a part-time student job.)
Why so? Yes it may seem difficult with lesser immigration friendly sentiments; however that shouldn't deter you.
You haven't mentioned your current situation, your experience etc to give more tailored suggestions. However, if making a living is not a concern for you in Nepal, then that gives you the freedom to pursue contributing to open source projects in subjects/areas (graphics programming may be) of your choice.
Otherwise based on your experience, you can apply to companies in UK and Europe, many will sponsor if you have the right skills and experience. That takes a while but it's not impossible.
Have you explored India as an option as Nepal and India have free trade movement and Banglaore/Hyderabad/Pune are great options if you focus on product and FAANG companies there. This may in fact be an easier route to get valuable experience in a reputed company.
>> My age is 28...
And 28 is hardly the age really to worry about moving/not moving, unless there are compelling reasons like having to stay back for strong personal reasons.
Also, even if your visa is rescinded on short notice, and you must leave immediately, you would likely earn more abroad than you can in your home country, right? What you've earned and not spent can likely help your future at home... Maybe it's enough to start a company at home where you can use your STEM skills. The experience you've gotten and the network you've built might possibly enable working remotely.
All that said, STEM fields vary widely. Many fields need tremendous capital to do 'great things', computer science does for some things, but not for others.
Have you looked at online CS programs, like the Georgia Tech one which is very serious and taught by top faculty. Good luck with whatever you do.