The French government pulled out most of the stops today to greet Rene Levesque, the separatist premier of Quebec.

In contrast to the highly negative reaction in France 10 years ago when French President Charles De Gaulle put Quebec separation on the international map with the slogan "Long live free Quebec," support in France for Quebec separation now stretches across the entire political spectrum.

All the parties in the National Assembly, from the Communists to the Gaullists, joined to give Levesque a reception that went far beyond the protocol usually accorded to visiting heads of government.

Napoleon's Stairway to the visitors' gallery, which had not been used since the reign of King Louis XVII, was opened for Levesque. Of his major requests, the only one which the French government seemed to hold back was his desire to speak from the pedium of the National Assembly, a privilege last accorded in 1919 to U.S. President Woodrow Wilson.

Instead, Levesque was invited to meet and address the assemblymen in an adjoining chamber, where the French deputies warmly applauded his statement that "a new country will soon be put on the map democratically."

He spoke of Quebec independence coming within 2 1/2 years.

The most striking change has been in the attitude of French President Valery Giscard D'Estaing who is said to have become an ardent supporter of the Quebec cause under the influence of Justice Minister Alain Peyre fitte, the first French Cabinet minister De Gaulle sent to Quebec to follow up on his "Long live free Quebec" speech. At that time, Giscard D'Estaing did nothing to hide his opinion, shared with then Prime Minister Georges Pompidou and most of the Cabinet that De Gaulle's unexpected outcry was the raving of an old man gone politically dotty.

Thursday, Giscard is scheduled to give a luncheon for Levesque with another exchange of warm speeches French state radio rebroadcast today De Gaulle's words of 10 years ago. Yesterday, the radio ran a long interview with Levesque after his soleum visit to De Gaulle's tomb.

Levesque spoke with fervor about De Gaulle as the first foreign leader to have adopted the cause of Quebec.

Some French editorialists and some French diplomats spoke of their government's caution and its desire not to offend the Canadian government. One commentator went so far as to suggest that the Giscard governemt is hanging back because if fears giving indirect encouragement to the growing separatist movements in Corsica and Brittany.

But another paris newspaper headlined "France Consecrates Levesque" and Le Figaro, the traditional newspaper of the French bourgeorsie headlined "France's Second Yes to Free Quebec."

Canadian Prime Minister Pierre Elliot Trudeau has warned that the Ottawa government would react if France showed sympathy for Levesque's policies. With this obviously on his mind, Justice Minister Peyre fitte proffered a summary of French policy toward Canada in the guise of an olive branch describing it as one of "non interference and of non indiffernce."

His reception here gives Levesque a trans-Atlantic platform that may impress Quebec voters when they cast their ballots in the independence referendum he has promised. Aside from that it remains to be seen what material help France can provide in unemployment-ridden Quebec. Since this country too is in the throes of an economic crisis.

After De Gaulle's original campaign for a free Quebec Canadians complained bitterly that not much had come of French promises of and an investment.