I will now describe how we plan to use the images downloaded from Adobe Stock.
Our adult game is a free-to-download app with in-game purchases but as mentioned before we will not be directly selling the pictures from Adobe Stock. The images downloaded are to be included in the game as minor content and will not be the key selling point. We will be preferably using them in game without modification.
The images themselves will only be that of 2d silhouettes, landscapes (for e.g the Manhattan bridge in New York, or the Taj Mahal in India), unbranded adult items (sex toys) but NO real persons, logos or brands in our adult game.
Therefore we would like to know whether Adobe Stock possesses the rights to all the images on it's website, including the right to sub-license it to us for its intended use as mentioned above.
I would be more than happy to provide you with a sample of how we plan to use the downloaded images in the game through a secured email address.
Look forward to your response as soon as possible.
https://stock.adobe.com/license-terms has the information you are looking for. If you have specific questions about the terms and your use of Adobe Stock content then please consult an attorney. It is in your business' best interest to do so.
It looks like correct use based on your description, but as you mention "adult" it may well be outside of Adobe's terms. Noone here can and is willing to give you a yes/no answer for this. At the end the IP auttorney would be the cheapest solution.
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on fair use for both the buyer and the artist/stock company, but I can not rule out that my interpretation is wrong. I'm not an Adobe employee)