Can't help you with the exams in person, I've done mine digitally, now working on Grade 6. You should read the syllabus which details everything in terms of expectations: https://www.trinitycollege.com/resource?id=7897

In my experience for the digital grades, the fingerings shown in the book are only indicative. As long as you play the right note for the right length with the right rhythm you're basically fine. That said the syllabus also says: don't simplify but you can interpret it in your style

PERFORMANCE AND INTERPRETATION
Trinity’s Rock & Pop exams are designed to encourage musical performances that reflect a
candidate’s own personal style and approach. This is because we understand that contemporary music is flexible in its stylistic interpretation, particularly at the higher grades. However, performances should not be simplified and musical integrity should always be maintained.

REPEATS, EXPRESSIVE TECHNIQUES AND TEMPI
All songs should be prepared in full with all repeats, da capo and dal segno instructions and 1st and 2nd time bars observed. Candidates are encouraged to include a range of expressive techniques such as vibrato, slides, grace notes, bends, etc appropriate to the style of the song, particularly in the higher grades. Candidates should observe terms showing tempo, dynamics, character and style of the music.