The dependent child age is up to 18 years. Once the child is older than 18, you may be able to claim them if they have a mental or physical infirmity.
https://www.olympiabenefits.com/blog/claiming-dependents-on-taxes-in-canada-who-is-eligible
Click on Interview setup
Click the blue circle in the Pension box
Click the + sign by T4A Pension, retirement ... (the top one)
Fill in the issuer and box 22
Half way down the form you'll find OTHER INFORMATION
Open the box to find box 107.
I think you are right, it's only the simplified method that has the 3 country limit. I've never held in more than 3 countries at once so never thought about it. However, in UFile it's simple to keep adding countries.
If the shares are "held in an account with a Canadian registered securities dealer", the individual companies don't have to be listed, only aggregate amounts for the top three countries.
If it is listed here then under medical costs:
https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/lines-33099-33199-eligible-medical-expenses-you-claim-on-your-tax-return/details-medical-expenses.html
There is a deduction from medical expenses to determine the amount that can be claimed.
Line 33099 – You can claim the total of the eligible expenses minus the lesser of the following amounts:
$2,421
3% of your net income (line 23600 of your tax return)