Can i play Pokémon Sword?

My laptop specs are:
2GB Ram
Intel celeron 2957U @1.4GHz
If not, then will i be able to play at least Pokémon let’s Go Pikachu?

In order for us to provide better support, we need to see the log generated by Citra. This guide will walk you through how you can obtain the log file: How to Upload the Log File.

You are bellow minimum requirements, this affects all games, as the requirements are for the emulation of the whole console, not just individual games.
You lack RAM, and the integrated Intel GPU on that Celeron lacks the OpenGL version needed to run yuzu. Sorry, there’s no way to run it with that laptop.

I have opengl 4.2. will it work?

you need opengl 4.3 as well as 8gb ram for minimum performance…

On Intel GPUs, you need Gen 8 or newer (with gen 8 only working on Linux drivers). Your Gen 7 integrated GPU is not enough, nothing to do about that.
Also, 4GB of RAM would already be too little, 2GB doesn’t leave room for anything.

What if i use Nvidia Gforce gpu.
If not, then is there any way to update my intel gpu to gen 8

You need at least a more recent GPU, be it Nvidia or AMD (but Nvidia is recommended), and additional 6GB of RAM to get a total of 8GB. Even with all that, expect low performance due to the CPU being older and not performance focused.

Is there any way to update my existing laptop specifications?

Nope, you can only change RAM and the hard drive on your laptop. If you want to upgrade components, you need a desktop PC.