Purchase events sent via the measurement protocol do not have any properties. "not set"

Question

For the past two months, I have been trying to set up event tracking through the Measurement Protocol. My ultimate goal is to track conversions in Google Ads for setting up smart campaigns. I send the "timestamp_micros" value because the purchase event is not sent when the user is on the website (which is why I need to use the Measurement Protocol). I need to send events manually because it can actually only be sent after a period of time. I followed Google's recommendations for sending events here.

I came across this Google announcement here and started passing the session_id parameter in the hope of getting properties for my event similar to the entire session. However, all the properties of the purchase event, except for the "source channel" (which seems to be determined correctly) and the platform "desktop," are in a "not set" status. I mean properties such as screen size, browser, language, geographical location, and so on.

My code looks like this:

{
"client_id": "6347566[[.169xx64812",
"timestamp_micros": "1694970938000000",
"events": [
{
"name": "purchase",
"params": {
"session_id": "16949648xx",
"transaction_id": "НФНФ-004565",
"value": "535",
"currency": "UAH",
"items": [
{
"item_id": "MIDEL7987",
"item_name": "15Х4,5 см",
"currency": "UAH",
"price": "535",
"quantity": 1
}
]
}
}
]
}

1. From what I can determine, Google has not yet fully implemented the Measurement Protocol for Google Analytics 4, and there may not be a solution to my problem at this time. I would greatly appreciate it if there is a solution to how I can get all the properties of my event for Google Analytics 4.

2. As far as I understand, in the Measurement Protocol for Google Analytics Universal, all parameters can only be passed individually. Is there no way to pass all parameters based on the session? I couldn't find instructions on how to send events in the past with the Measurement Protocol for Google Analytics Universal; is this possible? Please provide documentation if available.

3. Am I correct in understanding that if I send conversions from Google Analytics 4 to Google Ads without property values (such as location, language, browser, etc.), the automated bidding system will perform much worse because it won't have signals to rely on? P.S. I am already sending these conversions to Ads and have switched campaigns to use this conversion with the "conversion value" bidding strategy. I can already see the correct conversion values. But do I understand correctly that Ads currently lacks signals for proper optimization if I'm not sending them explicitly? Is it possible that Ads somehow searches for signals based on client IDs, or is this not possible?