Won't someone "scoop" me if I post my work as a preprint?
A preprint is date-stamped, which makes it easy to claim priority. Some journals also offer "scoop protection", which means that they will still consider the preprinted paper to be "first", if another paper was published since submission.
Do all journals accept preprinted papers?
The vast majority of psychology journals accept papers that have deposited on a recognised preprint server, such as Open Science Framework. However, it is worth double-checking the specific policy of each journal as some allow this with some minor conditions. For example, some journals request a link to the preprint in the "author note" section of a manuscript or in the submission cover letter. Sherpa-Romeo is a useful tool for checking sharing policies of journals.
What if I need to deviate from my pre-registration?
This is a very common occurrence. In most cases it is fine to deviate from your planned analysis, however, this deviation should be made explicit in your manuscript. For a guide on reporting pre-registration deviations, see Willroth et al., (2024)
I think my R/Python code is too messy to share
The most important thing is that your code can reproduce what's reported in your manuscript. "Messy" code that works is much better than not sharing code at all.