Is it illegal to promote slogans on designated products for national key R&D project demonstrations?

Illegal.

The State Administration for Market Regulation stated that using the name of "the country" to endorse corporate brands is suspected of violating the Advertising Law, the Anti-Unfair Competition Law, the Consumer Rights Protection Law and other laws. The Advertising Law explicitly prohibits the use of the names of state agencies and "national-level" terms in advertisements.