You could perform the workup using either using reductive conditions (best) or oxidative. Usual procedure is just to add dimethylsulfide at low temperature to destroy excess ozonide and then let it warm to room temperature.

I’ve seen the mechanism of both reductive and oxidative workup in the article but it seems like only the reductive one is possible because the extra oxygen in ozonide can leave with DMS, while in the oxidative one there’s one more oxygen needed to form the OH in the carboxylic acids. Now in the case of tetrasubstituted alkene, there’re no hydrogen to leave for the carbon to allow one more OH group on it. Is it right that I can’t use oxidant to workup the ozonide of tetrasubstituted alkene?

Yes, I would give it a shot. If you have access to the Sharpless AD-Mix that would be a good thing to try since the bulky ligands should keep your osmium away from the bulkier alkene.
See here:
https://hwpi.harvard.edu/files/myers/files/23-sharpless_asymmetric_dihydroxylation_reaction.pdf

Good question. You are indeed correct that greater alkene substitution favors a higher rate of ozonolysis,

Is your problem concerning selectivity on a molecule with multiple alkenes? Is this something that could be avoided through, say, a later-stage reduction of an alkyne to a cis or trans alkene (alkynes are generally slow to cleave with ozonolysis).

Methanal (formaldehyde) is quickly oxidized by H2O2 to give carbonic acid which itself loses water to give CO2 (carbon dioxide)

One of the products is methanal my note here in textbook concert it into CO2
Pls why

And not methanoic acid