Is it a must to write a paper in passive third person, for all types of papers in all journals?

Have a look at the style guide of the journal you're targeting. It has the only authoritative answer to your question.

Having said that, passive voice is not a "must" in the sense that active voice were unheard of in academic writing. Here is a paper written in active voice, first person singular.

Common preferences for either active or passive voice differ between disciplines. (I've heard that in mathematics the first person plural is fairly common, i.e. "we".)

Preferences also differ between authors. I find the first person singular active voice most authentic, simple, and lively. It is often emphasized, however, that passive voice sounds more neutral and objective.

When deciding which voice to use, consider the style guide first, then your discipline's customs (ask your peers!), and your personal preference last.

Papers may be written in whatever voice you choose :-)

Some journals might specify, but contra. @herring's answer, I don't recall any biomed journals requiring one or the other. Some "authorities" argue that this passive voice is less exciting or authentic. This is probably true in regular writing but makes methods sections a string of "I/We did X. Then we did Y. Then we did Z.", which is also jarring.

I suggest deciding based on what need to be emphasised in each sentence. Sometimes, the only important part of the sentence is the thing that was done. Use the passive voice there. For example, you might write something like:

After thawing, tissue samples were fixed in 4% PFC, dissolved in 1x PBS, for 15 minutes. They were then prepared for immunohistochemistry by washing them in 1x PBS (5 minutes), permeabilizing them (2X SSC for 5 minutes), and dehydrating them using a series of ethanol baths (70%, 95%, 99%, 100%; 5 minutes each).

Here, no one really cares who processed the tissue samples--it could be the first author, it could be the last author, or it could even be a robot or an external company. The reader cares about what was done.

Other times, the identity of the do-er is more important. These cases call for the active voice. Consider something like this:

Other Folks et al. (2016) collected data from a broad sample of cells. However, we hypothesised that this effect only occurs in a specific subpopulation of dividing cells. To test this, we used.... "

Because the text compares your work with someone else's, the reader cares about who did what. The active voice emphasises this, but maybe steals a little thunder from the actual action.