An Intel i5-8250u is built into my laptop, can I overclock and if so how?
No you can't. Only CPUs with the ending K can be overclocked.
Yes I know that but can't it be done without?
No it's not possible. That is the selling point for these CPUs. Intel would be so stupid to water down its own product.
No, the multiplier is blocked for this CPu. Only Intel processors with a K at the end can be overclocked.
This makes sense especially with laptops because the components are coordinated to prevent overheating.
No, normally the laptop's BIOS does not offer any overclocking functions. In addition, cooling and powering the laptop would not be suitable for the increased requirements of an overclocked CPU in many situations.
No, and it doesn't make sense for notebooks anyway, because the cooling usually throttles even the factory clock.
The answer is simple…
NO.
See also @asdundab and @Ireeb.