There is no way of deducing the fate of your manuscript with reasonable certainty except a decision letter that says so. In particular, if your manuscript is certain to be rejected, there is no reason for the journal to spend further time on it instead of immediately telling you.
In the vast majority of cases, you can apply the following line of thought:
The point of almost the entire editorial process is to find out whether your manuscript shall be accepted by the journal (or whether it has the potential to be accepted after modifications).
If at any time the editors decide that your manuscript is or is not suitable, the process is over.
At this point, there is no reason to delay informing you about this decision.
In particular, after rejection has been decided, it would be a waste to spend any further resources on this manuscript, such as further reviews or editorial assessment¹.
Therefore if your manuscript has been accepted or rejected, you will get to know this immediately.
From another perspective, you can always ask yourself: If the fate of my manuscript were already certain, would the journal act as it does?
Similar thoughts apply to requests for revision.
If the editors think a revision is impossible, they will not invite you to submit a revised version, as this revision would have to be assessed and thus waste resources if it already is clear that the manuscript cannot be accepted.
In fact, journals rather tend to phrase rejections overly strongly to avoid authors engaging in futile rebuttals, resubmissions, etc.
Journals have nothing to gain from hiding a negative assessment between the lines.
For example, if the editors think that acceptance of your manuscript is possible but requires a specific change, it would be foolish not to tell you this, lest you waste journal resources with a submission that does not make this specific change.
On the other hand, if the editors decided that they probably want your manuscript, it would be foolish to scare you away – though the editors may put a strong emphasis on changes they think are possible and necessary.
Exceptions and Similar
You have to judge yourself whether they apply to your case or the information benefits you:
The one thing that needs to happen between the decision and letting you know is the preparation of the decision letter, which particularly includes phrasing the rationale for a rejection or the conditions of a potential acceptance.
In many cases, this is a matter of minutes as it only requires the editor to combine a few canned sentences or the reviews already do a good job at explaining the problems of the manuscript or the changes needed.
But even if the editor spends effort on writing the decision letter, the best time to do this is right after the decision, as they are already focused on your manuscript.
For these reasons, the preparation of the decision letter is a very short stage, and moreover, most editorial systems do not inform you about it anyway.
Still, if you see this stage without any previous peer review, you can be rather certain that you are facing a desk reject.
However, it could also be that the editor wants you to perform certain changes to the manuscript before peer review.
Either way, once your manuscript entered this stage, you will get to know its fate very soon.
Certain events allow you a better estimate of your manuscript’s chances, but never a definite answer (for the aforementioned main argument):
For example, for some journals, making it to peer review is a major hurdle, and if your manuscript passed it, the chances of your manuscript considerably increase.
Similarly, if a manuscript goes from peer review to editorial decision and then back to peer review, this suggests that the reviewers have conflicting opinions about your manuscript, which may be good or bad news, depending on your a priori expectation of acceptance.
Also, there can be other reasons for a return to peer review, such as one of the reviews containing no valuable information at all, or all reviewers stating that they cannot evaluate a crucial part of the manuscript.
The editors or reviewers intentionally delay your manuscript, e.g., because of a grudge against you.
This is hopefully very rare, but even if this happens, you will usually only get to suspect this a posteriori, if at all.
If you suspected this a priori, you probably should not have submitted to that journal in the first place (or vetoed that editor).
¹ If those reviews have a potential of swaying the decision, it was not a decision in the sense of this answer.