PhD

Could someone explain what I need to prepare and when for my PhD application? I currently finished 2nd year for my undergraduate degree and starting my (last) 3rd year this september.

Competitively-funded PhD applications normally open around September/October time and close December/January. You will need an academic CV, a statement of motivation, a proposal (if you are not applying to a pre-outlined PhD, in which case you also need to identify potential supervisors and chat with them ahead of time), at least two academic references, and your degree certificate (or I suppose projected degree classification in your case) and transcript.

The process can vary depending on your field, but this is a rough summary of what I generally learned when applying.

Depends a lot on your field. I can speak pretty well for science (especially biology), I think this is relevant for you but possibly not.

For science PhD's, adverts are usually put out for funded PhD's that start in September 2022 from probably October this year. Most of the big funded ones will be advertised by the end of this year, but you will get the occasional one advertised throughout the start of next year as well (still to start in September/October next year). So you will be putting in your application during your final year

For science PhD's the project is largely determined so you won't have to write a proposal, but you will need a personal statement, academic CV and references. I should note that unless you've been able to get some decent level of lab experience elsewhere (e.g. placement year), you will really struggle to get into a PhD as they are extremely competitive. Most people will have some level of lab experience, from a masters degree, research tech position or placement year before they apply. I had to have a year working in a lab and a masters on top of my BSc before I could get an offer. If restrictions do start easing it should be easier to get lab experience so the expectation of having this will likely increase-something to consider before prepping applications.

I study Biomedical Sciences btw. I do a lab project during 3rd year, would that be enough for a lab experience or shall i apply for an internship or other potential lab work i can do next year summer?
Is the personal statement similar to the personal statement that year 13 write for undergraduate application?

No, the PS is much more specific to the research field and proposal for the work. It should highlight your personal motivations for the niche of your area and your expertise and what makes you suitably qualified to conduct this research.

(although a lot will depend on what type of PhD you go for, and if you require funding or not also funded places and funding applications tend to be the more competitive ones. General PhD places with no funding are a lot easier to get as you just need to convince a supervisor to take you and meet the minimum academic requirements).

Yes id apply for internships, a BSc with dissertation is really the bare minimum, their is a good chance you end up having to get a masters or do a research internship.

When should I request for the references or transcript?

I study Biomedical Sciences btw. I do a lab project during 3rd year, would that be enough for a lab experience or shall i apply for an internship or other potential lab work i can do next year summer?
Is the personal statement similar to the personal statement that year 13 write for undergraduate application?

You would send an email to ask two people to be your academic references ahead of time. Then, with each submitted application, you ask them to submit the academic reference. As for the transcript, probably best to get that after your second year grades have been finalised.

As others have mentioned here, however, you will struggle at this current stage to obtain a funded PhD due to your inexperience relative to others. Successful PhD candidates have already completed their degree and usually secured further research experience either through a masters or internship. So don't be downtrodden if you are not successful this year!