Walikum as salam
Jazakallah for kind words and apologies for the late reply as I was not able to visit the forum regularly.
Below thread should help you but let me knwo if you have any folloup questions.
-£9k is the max amount that you can put for the child. It’s usually best to put maximum upfront and regular investment is a good thing in my opinion. with current volatility due to Omricon/US fed policy change, maybe do £3k monthly instalment for this year and £750/month (assuming you want to max £9k every year) from April 2022.
- If you do plan to invest in both funds then make sure that you set up a regular investment by direct debit. MSCI is an ETF and not doing it via regular investing will attract a £9 transaction charge. on this point, I would say to assess the % that you would want to allocate to this fund? if let’s say you are going to put in 90% HSBC and 10% MSCI then based on £750/month, it would be HSBC=£675 and MSCI=£75. The monthly regular charge of £1.5 each fund/etf would therefore turn out to be HSBC = 0.15% and MSCI = 2% - Long story short it may be best to just put everything in HSBC as this is what I have also seen mainstream Junior ISA providers do.
NOTE: Just to let you know that equity is very volatile in nature and for some odd reason market comes down the next day one invest 
- your time horizon is long so don’t worry if the market comes down the next day - just relax and let it grow. It should catch up and in long run, you should be a winner inshallah.
Hope that helps but let me know if you have any follow up questions.
Good luck
Zeeshan