No, It says you have an 18 month period in which you must pass all the exams. That period begins at the end of the month in which you make your first attempt. It matters not whether you pass or fail that or any other exam the 18 months has begun and you must pass all 7 within that window. The 18 months can be reset to another start point if you don't meet the time frame. Once passed you have another 24 months to apply for a licence, 36 months in total.
Log hours towards my PPL
Go solo at 16 (with at least 15 hours)
No requirement for 15 hours, that is just a typical figure; RAF flying scholarship students went solo after 9 hours!
Do my skills test as soon as I have 45 hours and have the adequate training when I am 16
You only need the 35 hours training to take the Skill test; 45 is for licence issue.
Be issued with a license when I am 17
Well researched.